1. FIELD OF THE INVENTION
This invention relates to improvements in relative humidity detectors, and, more particularly, to an improved humidity detector for measuring relative humidity between zero and 100% by changes in its electrical impedance, and methods for making same.
2. DESCRIPTION OF THE PRIOR ART
Humidity sensors of the type which change resistance and/or capacitance have been proposed. Ordinarily, the sensors heretofore advanced employ a first layer of metal, a layer of hygroscopic material such as aluminum oxide or the like, and a second layer of metal, typically gold, formed over the aluminum oxide in the form of a sandwich. The second layer is ordinarily sufficiently thin to allow water molecules to pass therethrough to the hygroscopic layer, causing changes in the impedance between the first and second metallic layers.
In the humidity detectors heretofore used, although the response has been relatively good over the desired humidity range of interest, for instance, zero to 100%, it is ordinarily not precisely linear over the entire humidity range to be measured. Therefore, ordinarily, additional corrective elements must be used in association with the impedance measuring or detecting circuitry to correct for these variations.
Also, the devices heretofore advanced are of relatively large dimensions, and are not suitable for many microminiature circuit applications.